When using microscopes, e.g. operating microscopes, particularly in microsurgery, there has long been a need for the operator, particularly the surgeon or person performing the operation, not to have to look directly through the eyepieces of the microscope but to have a substantially unimpeded view of the operating area and at the same time to see an enlarged image of the operating area. It should be noted that such needs apply particularly also to stereomicroscopes, used in both medical and technical fields. Microscopes of this kind have hitherto been referred to as free-view microscopes.
The first steps in this direction were taken by the company Vision Engineering using the “Isis” microscope system. In this system the user does indeed look through two eyepieces, but the considerable distance of the eyes from the eyepieces and the large exit pupil allow him to move relatively freely in front of the eyepieces. A similar system produced by this company and marketed under the name “Mantis” is also known. In the latter the user looks at a large field of vision for both eyes through a common Fresnel plate.
Reference should also be made to developments in the field of graphic representation using displays which enable data and images to be made stereoscopically visible to an operator directly over an operating field. A system of this kind was exhibited by the Fraunhofer-Institut INK at the trade fair MedTech 2003 in Stuttgart. In it, a display screen can be positioned over an operating field by means of a support arm. The display screen is freely movable by hand. Its position in space is located by sensors and correlated with images displayed on the display screen, for example X-ray images. The observer can view these displayed images stereoscopically through stereospectacles and at the same time study the operating area through the partly transparent display screen. When the user changes the position of the display screen over the operating area, the viewed position of the correlated X-ray images also changes accordingly.
A system of this kind is described in EP 0918491 B1.
However, it is not possible to carry out microsurgery by the method described therein as only data and images obtained pre-operatively can be shown on a display.